I finally found a DVD of Miss Saigon from a friend. It is the version of the performance at Fullerton Civic Light Opera on September 16, 2005. It is the only one I can find with the full stage performance of Miss Saigon, but I don't like the actors very much.
Some months ago, I got a DVD The Heat Is On: The Making of 'Miss Saigon', which describes the first performance of the musical in 1989, with Lea Salonga playing Kim. However, The Heat Is On contains just some pieces of the whole musical, and I cannot get a general idea.
Lea played Éponine in the Les Misérables: The Dream Cast in Concert in 1998. I like her very much, even more than the roles of Fantine and Cosette.